Two channel azimuth and two channel non-azimuth read-after-write longitudinal magnetic head

ABSTRACT

A read-after-write head for four channel azimuth recording in one mode of operation and two channel non-azimuth recording in another mode of operation. Four forward write head gaps, four read head gaps, and four backward write head gaps are geometrically positioned within a rotatable and laterally indexable face plate of a recording head housing. The read and write heads gaps collectively provide four forward write channels, four read channels, and four backward write channels. During the azimuth mode of operation, the head is rotated to the preselected positive or negative azimuth angle and all of the read and write channels are utilized. During the non-azimuth, or vertical, mode of operation, write channels two and four are utilized in combination with read channels one and three to provide two-channel non-azimuth, or vertical, operation.

REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/009,708, filed on Jan. 11, 1996.

FIELD OF THE INVENTION

This invention relates in general to magnetic storage devices. Moreparticularly this invention relates to a method and apparatus thatefficiently provides azimuth as well as non-azimuth recording in alongitudinal magnetic tape recording system.

BACKGROUND OF THE INVENTION

The constantly increasing operational speeds of digital computers arecreating a demand for corresponding increases in the data storagecapacities of magnetic tape recording and reproducing systems, whilemaintaining the special requirements of high speed digital tape systems.

It is desirable that tape recording and reproducing systems for use ascomputer data storage devices provide high data transfer rates andperform a read check on all written data. Toward those ends,conventional tape systems typically employ methods of recording known aslongitudinal recording, as illustrated in FIG. 1a, in which the tracksof data lie parallel to each other and parallel to the edges of thetape; or helical scan recording, as illustrated in FIG. 1b, in which thetracks of data lie parallel to each other but diagonal to the edges ofthe tape. The longitudinal recording method offers higher data transferrates; but it would be desirable to obtain still higher data densitieswhile retaining the advantages of the longitudinal recording method.

One limitation on track densities is crosstalk, which occurs whenreading of data from one track is interfered with by data recorded on anadjacent track. Crosstalk is further exacerbated by error in head gapalignments. Some methods have been implemented to reduce this effect,such as leaving guard bands between tracks, or by using wider write headgaps. These methods, however, also tend to limit track densities,thereby limiting data densities.

A method of recording known as azimuth recording has been used inhelical scan systems in order to decrease the effects of crosstalk andthus increase the track density of these systems. Azimuth recordingresults in a recorded track pattern in which the magnetizationdirections of adjacent data tracks lie at different azimuth angles toeach other, as illustrated in FIG. 1c. This method greatly reducesinter-track crosstalk, enabling tracks to be placed closer together. Theneed for guard bands or wide write heads is thus reduced or eliminated.The helical scan method, however is subject to limited data transferrates.

SUMMARY OF THE INVENTION

The present invention reduces the effects of one or more of the problemsset forth above. In particular, the present invention provides aread-after-write longitudinal recording head so configured and operatedas to be capable of four channel azimuth recording and playback, as wellas two channel non-azimuth recording and playback operation, therebyenabling newer tape recorders equipped with the head to performmore-efficient four channel azimuth recording and playback, as well asto perform the older, less-efficient two channel non-azimuth recordingthereby providing a backward compatibility with tapes recorded on theolder generation of non-azimuthal longitudinal tape recording machines.

In accordance with one aspect of the present invention, aread-after-write tape recording head is provided which operates in afirst mode to provide four channel azimuth recording and also operatesin a second mode to provide two channel non-azimuth recording onto amagnetic tape recording medium.

These and other objects, advantages, aspects and features of the presentinvention will be more fully understood and appreciated uponconsideration of the following detailed description of a preferredembodiment, presented in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the Drawings:

FIGS. 1a, 1b, and 1c illustrate respectively longitudinal, helical, andazimuth recording methods known in the art.

FIG. 2 is a front view of the bottom face of one embodiment of theread-after-write head of the present invention including four writeheads for forward writing, four write heads for backward writing, andfour read heads for read-after-writing and regular reading with the readand write heads positioned to permit operation in four-channel azimuthmode and two channel non-azimuth mode.

FIG. 3 illustrates writing onto a magnetic tape recording medium usingthe read-after-write head of FIG. 2 in a four channel azimuth mode ofoperation with the read-after-write head rotated approximately 9.4degrees from the vertical direction.

FIG. 4 illustrates writing onto track zero of the magnetic taperecording medium of FIG. 3 using the channel four write head gap of theread-after-write head of FIG. 2 in the four channel azimuth mode ofoperation.

FIG. 5 illustrates writing onto longitudinal tracks zero, one, two, andthree of the magnetic tape storage medium in sequence using the channelfour forward and backward write head gaps of the read-after-write headof FIG. 2 in the azimuth recording mode of operation.

FIG. 6 illustrates reading tracks zero, one, two, and three of themagnetic tape storage medium using the channel four read head gap of theread-after-write head of FIG. 2 in the azimuth recording mode ofoperation and also indicating the direction of tape motion during thismode of operation.

FIG. 7 illustrates writing onto the magnetic tape storage medium usingwrite channels two and four of the read-after-write head of FIG. 2 withregular read and read-after-write provided by read channels one andthree in the two channel non-azimuth recording mode of operation.

FIG. 8 illustrates reading the magnetic tape storage medium using readchannel one of the read-after-write head of FIG. 2 in the non-azimuthmode of operation.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The following descriptions of illustrative embodiments of the inventionare presented as a description of structural elements contained in anillustrative apparatus and as operational steps performed in anillustrative method. The descriptions are derived from certain claims inthe application as originally filed, but of course the claims are notintended and should not be deemed to be limited to the illustrativeembodiments so described.

It is to be understood that the particular implementations described areintended as illustrations of, and not as limiting the scope of, theclaims. In the interest of clarity, not all the routine features of theimplementations are described. It will be appreciated that in thedevelopment of any such actual implementation, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals such as compliance with system and businessrelated constraints and that these goals will vary from oneimplementation to another. Moreover, it will be appreciated that such adevelopment effort might be complex and time-consuming, but would neverthe less be a routine undertaking of engineering for those of ordinaryskill having the benefit of this disclosure.

FIGS. 2-8 show the context of an illustrative longitudinal recordingapparatus implementing a read-after-write head 100 for recordinginformation onto and reading information from a magnetic tape storagemedium (not shown) moving past the head 100 in a longitudinal forward orreverse direction. The magnetic tape storage medium stores informationby means of particulate matter on (or in close proximity to) its surfacethat is selectively magnetized. The write head gaps "write" data ontothe magnetic tape by selectively magnetizing the particulate matter in awell known manner, while the read head gaps "read" the magnetization ofthe particulate matter in a well known manner. The magnetic tape isdrawn longitudinally past the head 100 in forward and reverse directions(in alignment with axis x of FIG. 2).

As is well known in the art, a read-after-write head provides errordetection after writing in a given direction on a specific channel bymeans of a write head gap with a read head gap positioned in substantialalignment with the longitudinal direction of the magnetic tape medium onthe specific channel. The read-after-write head 100 records informationonto, and reads information from, longitudinal tracks defined on themagnetic tape storage medium either in a four-channel azimuth mode, orin a two-channel non-azimuth mode. The read-after-write head 100 whileoperating in two-channel non-azimuth mode provides backwardcompatibility with existing non-azimuthal tape recording devices andwith tapes recorded on such devices.

Generally speaking, the read-after-write head 100 provides four-channelazimuthal recording as well as two-channel non-azimuthal recording byfollowing the FIG. 2 geometric layout of four forward write head gaps104, 106, 108 and 110, four read head gaps 112, 114, 116 and 118, andfour backward write head gaps 120, 122, 124 and 126. Theread-after-write head 100 may be utilized in the azimuth and non-azimuthmodes of operation by its use in conjunction with a conventional tapehead controller that provides indexing of the tape head laterally across(along axis y in FIG. 2) the magnetic tape medium as well as rotation ofthe tape head relative to the tape for azimuth or non-azimuth operation.An exemplary head positioning structure is described in commonlyassigned, copending U.S. patent application Ser. No. 08/557,662 to KumarKasetty, filed on Nov. 13, 1995 and entitled: "Tape Drive HeadPositioning Device for Adjusting Head Tilt And Azimuth", the disclosureof which is incorporated herein by reference; and, an exemplary headcontroller is described in U.S. Pat. No. 5,307,217, issued toco-inventor George A. Saliba, on Apr. 26, 1994, the disclosure of whichis also incorporated herein by reference.

As shown in FIG. 2, the read-after-write head apparatus 100 generallycomprises a surface 102. In one illustrative embodiment, the surface 102comprises a face plate which provides a rigid supporting structure forthe read and write head gaps. The face plate will be attached to aconventional read-after-write head housing which in indexed laterallyacross the surface of the magnetic tape and also rotated to provideazimuth or non-azimuth modes of operation in a well known manner by atape recorder controller of the type disclosed in U.S. Pat. No.5,307,217 issued to George A. Saliba.

The surface 102 defines first 104, second 106, third 108, and fourth 110laterally spaced apart forward-direction write head gaps including upperedges 104a, 106a, 108a, and 110a, lower edges 104b, 106b, 108b, and110b, upper portions 104c, 106c, 108c, and 110c, and lower portions104d, 106d, 108d, and 110d opening into the surface 102. The forwardwrite head gaps 104, 106, 108, and 110 write data onto the magnetic taperecording medium in a well known manner during movement of the magnetictape in the forward direction indicated by the arrow 205 in FIG. 3. Inthe four-channel azimuthal mode the forward direction write head gaps104, 106, 108, and 110 provide four forward write channels numberedconsecutively 1, 2, 3, and 4 from top to bottom and simultaneously writeto four longitudinal tracks defined on the forward moving magnetic tape.

The surface 102 also defines first 112, second 114, third 116, andfourth 118 laterally spaced apart backward-direction write head gapsincluding upper edges 112a, 114a, 116, and 118a, lower edges 112b, 114b,116b, and 118b, upper portions 112c, 114c, 116c, and 118c, and lowerportions 112d, 114d, 116d, and 118d opening into the surface 102 andspaced apart from the forward write head gaps 104, 106, 108, and 110.The forward write head gaps 104, 106, 108, and 110 and the backwardwrite head gaps 112, 114, 116, and 118 are laterally offset. Thebackward write head gaps 112, 114, 116, and 118 write data onto themagnetic tape recording medium in a well known manner during movement ofthe magnetic tape in a direction opposite to that indicated by the arrow205 in FIG. 3. In this manner, the backward-direction write head gaps112, 114, 116, and 118 provide four backward write channels numberedconsecutively 1, 2, 3, and 4 from top to bottom and simultaneously writeto four additional longitudinal tracks defined on the reverse movingmagnetic tape.

The surface 102 also defines first 120, second 122, third 124, andfourth 126 laterally spaced apart read head gaps including lower edges120a, 122a, 124a, and 126a opening into the surface 102 and locatedbetween the forward write head gaps 104, 106, 108, and 110 and thebackward write head gaps 112, 114, 116, and 118. The read head gaps 120,122, 124, and 126 extend generally parallel to, and are laterally offsetfrom, the forward head gaps 104, 106, 108, and 110 and backward writehead gaps 112, 114, 116, and 118 and are unequally spaced apart from theforward write head gaps 104, 106, 108, and 110 and the backward writehead gaps 112, 114, 116, and 118. The read head gaps 120, 122, 124, and126 read data from the magnetic tape recording medium in a well knownmanner during movement of the magnetic tape in either direction. In thismanner, the read head gaps 120, 122, 124, and 126 provide fourforward/backward read channels numbered consecutively 1, 2, 3, and 4from top to bottom.

The read head gaps 120, 122, 124, and 126 are positioned between theforward write head gaps 104, 106, 108, and 110, and the backward writehead gaps 112, 114, 116, and 118. The read head gaps 120, 122, 124, and126 may or may not be equally spaced from the forward and backward writehead gaps depending upon the particular geometry influenced by the needfor backward compatibility with existing model tape recording devices.

As illustrated in FIG. 3, during the azimuth mode of operation with theread-after-write head 100 rotated positively relative to the verticaldirection, the four forward write head gaps 104, 106, 108, and 110(forward write channels one to four) and the four read head gaps 120,122, 124, and 126 (read channels one to four) are substantially alignedwith the longitudinal direction of the magnetic tape medium.Furthermore, the four read head gaps 120, 122, 124, and 126 (readchannels one to four) are also positioned to provide read-after-writefor the four forward write head gaps 104, 106, 108, and 110 (forwardwrite channels one to four) to thereby provide a four channelread-after-write recording head. Likewise, during the azimuth mode ofoperation with the read after-write head 100 rotated negatively relativeto the vertical direction, the four backward write head gaps 112, 114,116, and 118 (backward write channels one to four) and the four readhead gaps 120, 122, 124, and 126 (read channels one to four) aresubstantially aligned with the longitudinal direction of the magnetictape medium. Furthermore, the four read head gaps 120, 122, 124, and 126(read channels one to four) are positioned to provide read-after-writefor the four backward write head gaps 112, 114, 116, and 118 (backwardwrite channels one to four) to thereby provide a four channelread-after-write recording head. Thus, the read-after-write head 100provides four channel azimuth operation in both directions of tapemotion.

As illustrated in FIG. 7, during the non-azimuth (or vertical) mode ofoperation with the read-after-write head 100 in the neutral (or verticalposition), the channel two forward write head gap 106, the channel oneread head gap 120, and the channel two backward write head gap 114 aresubstantially aligned with the longitudinal direction of the magnetictape medium, and the channel four forward write head gap 110, thechannel three read head gap 124, and the channel four backward writehead gap 118 are substantially aligned with the longitudinal directionof the magnetic tape medium. Furthermore, the channel one read head gap120 is also positioned in opposing relationship to the upper portion106c of the channel two forward write head gap 106 and also in opposingrelationship to the lower portion 114d of the channel two backward writehead gap 114 while the channel three read head gap 124 is positioned inopposing relationship to the upper portion 110c of the channel fourforward write head gap 110 and also in opposing relationship to thelower portion 118d of the channel four backward write head gap 118. Inthis manner, the read-after-write head 100 provides a two-channelread-after-write recording operation in the non-azimuth mode ofoperation for tape motion in both directions using write channels twoand four and read channel one and three.

The first read head gap 120 is positioned in opposing relationship tothe upper portion 106c of the second forward write head gap 106 and thelower portion 114d of the second backward write head gap 114. Asillustrated in FIGS. 2 and 7, the channel one read head gap 120 ispositioned in opposing relationship to the upper portion 106c of thechannel two forward write head gap 106 and also in opposing relationshipto the lower portion 114d of the channel two backward write head gap114.

The third read head gap 124 is positioned in opposing relationship tothe upper portion 110c of the fourth forward write head gap 110 and thelower portion 118d of the fourth backward write head gap 118. Asillustrated in FIGS. 2 and 7, the channel three read head gap 124 ispositioned in opposing relationship to the upper portion 110c of thechannel four forward write head gap 110 and also in opposingrelationship to the lower portion 118d of the channel four backwardwrite head gap 118.

An angle 128 between a line 130 tangent to the lower edge 104b of thefirst forward write head gap 104 and the lower edge 120a of the firstread head gap 120 and a line 132 perpendicular to gap 104 at the loweredge 104b is substantially equal to an angle 134 between a line 136tangent to the lower edge 112b of the first backward write head gap 112and the lower edge 120a of the first read head gap 120 and a line 138perpendicular to gap 112 at the lower edge 112b. As illustrated in FIGS.2 and 5, the geometric relationship between the channel one forwardwrite head gap 104, the channel one read head gap 120, and the channelone backward write head gap 112 positions the channel one read head gap120 to provide read-after-write (and regular read for that track) forthe channel one forward write head gap 104 during positive rotation ofthe read-after-write head 100 to the preselected azimuth angle andread-after-write (and regular read for that track) for the channel onebackward write head gap 112 during negative rotation of theread-after-write head 100 to the preselected azimuth angle. Positiverotation of head 100 is in a counter-clockwise sense while negativerotation is in a clockwise sense, as shown in FIG. 3.

An angle 140 between a line 142 tangent to the lower edge 106b of thesecond forward write head gap 106 and the lower edge 122a of the secondread head gap 122 and a line 144 perpendicular to gap 106 at the loweredge 106b is substantially equal to an angle 146 between a line 148tangent to the lower edge 114b of the second backward write head gap 114and the lower edge 122a of the second read head gap 122 and a line 150perpendicular to gap 114 at the lower edge 114b. As illustrated in FIGS.2 and 5, the geometric relationship between the channel two forwardwrite head gap 106, the channel two read head gap 122, and the channeltwo backward write head gap 114 positions the channel two read head gap122 to provide read-after-write (and regular read for that track) forthe channel two forward write head gap 106 during positive rotation ofthe read-after-write head 100 to the preselected azimuth angle andread-after-write (and regular read for that track) for the channel twobackward write head gap 114 during negative rotation of theread-after-write head 100 to the preselected azimuth angle.

An angle 152 between a line 154 tangent to the lower edge 108b of thethird forward write head gap 108 and the lower edge 124a of the thirdread head gap 124 and a line 156 perpendicular to gap 108 at the loweredge 108b is substantially equal to an angle 158 between a line 160tangent to the lower edge 116b of the third backward write head gap 116and the lower edge 124a of the third read head gap 124 and a line 162perpendicular to gap 116 at the lower edge 116b. As illustrated in FIGS.2 and 5, the geometric relationship between the channel three forwardwrite head gap 108, the channel three read head gap 124, and the channelthree backward write head gap 118 positions the channel three read headgap 124 to provide read-after-write (and regular read for that track)for the channel three forward write head gap 108 during positiverotation of the read-after-write head 100 to the preselected azimuthangle and read-after-write (and regular read for that track) for thechannel three backward write head gap 116 during negative rotation ofthe read-after-write head 100 to the preselected azimuth angle.

An angle 164 between a line 166 tangent to the lower edge 110b of thefourth forward write head gap 110 and the lower edge 126a of the fourthread head gap 126 and a line 168 perpendicular to gap 110 at the loweredge 110b is substantially equal to an angle 170 between a line 172tangent to the lower edge 118b of the fourth backward write head gap 118and the lower edge 126a of the fourth read head gap 126 and a line 174perpendicular to gap 118 at the lower edge 118b. As illustrated in FIGS.2 and 5, the geometric relationship between the channel four forwardwrite head gap 110, the channel four read head gap 126, and the channelfour backward write head gap 118 positions the channel four read headgap 126 to provide read-after-write (and regular read for that track)for the channel four forward write head gap 110 during positive rotationof the read-after-write head 100 to the preselected azimuth angle andread-after-write (and regular read for that track) for the channel fourbackward write head gap 118 during negative rotation of theread-after-write head 100 to the preselected azimuth angle.

Thus, the angles 128, 134, 140, 146, 152, 158, 164, and 170 are allsubstantially equal to the selected azimuth angle thereby to provideproper alignment of the forward write head gaps, read head gaps, andbackward write head gaps during the four-channel azimuth mode ofoperation.

The method of the present invention advantageously enables a singleconventional tape recording apparatus to selectively provide azimuth andnon-azimuth modes of operation. The read-after-write head 100 may becontrollably positioned (including the conventional recording headmotions of indexing and rotation) by adapting a conventional taperecording machine to incorporate the control system disclosed in U.S.Pat. No. 5,307,217 issued to George A. Saliba. Such a control system isadapted in a known manner to provide azimuth and non-azimuth (orvertical) operational control of the read-after-write head 100 as, forexample, in accordance with a head positioning structure described inthe commonly assigned, copending U.S. patent application Ser. No.08/557,662 referred to above.

As illustrated in FIGS. 3-6, in the azimuth mode of operation the readafter-write head 100 is indexed to a preselected position over theselected tracks of the magnetic tape medium which is moving in a forwarddirection (as indicated by the arrow 205 in FIG. 3) relative to theread-after-write head 100. The read-after-write head 100 is then rotatedto the preselected positive azimuth angle. In this position, the forwardwrite head gaps 104, 106, 108, and 110 (forward write channels 1-4) aresubstantially aligned with the longitudinal direction of the movingmagnetic tape medium. Furthermore, the read head gaps 120, 122, 124, and126 (read channels 1-4) are also substantially aligned with thelongitudinal direction of the moving magnetic tape medium and alsopositioned to provide read-after-write (and regular read for thosetracks) for the forward write head gaps 104, 106, 108, and 110. Theread-after-write head 100 may now write to the tracks of the movingmagnetic tape medium and/or read the tracks of the magnetic tape mediumin a well known manner

The tape direction is then selectively reversed to move the backwarddirection (opposite to the direction indicated by the arrow 205 in FIG.3). The read-after-write head 100 is again indexed to anotherpreselected position over the selected tracks of the magnetic tapemedium which is now moving in the backward direction (as indicated by adirection opposite to the arrow 205 in FIG. 3) relative to theread-after-write head 100. The read-after-write head is then rotated tothe preselected negative azimuth angle. In this position, the backwardwrite head gaps 112, 114, 116, and 118 (backward write channels 1-4) aresubstantially aligned with the longitudinal direction of the movingmagnetic tape medium. Furthermore, the read head gaps 120, 122, 124, and126 (read channels 1-4) are also substantially aligned with thelongitudinal direction of the moving magnetic tape medium and alsopositioned to provide read-after-write (and regular read for thosetracks) for the backward write head gaps 112, 114, 116, and 118. Theread-after-write head 100 may now write to the tracks of the movingmagnetic tape medium and/or read the tracks of the magnetic tape mediumin a well known manner.

This operation is selectively controlled in a well known manner by thetape recorder control system. As illustrated in FIG. 5, the azimuth modetypically produces a criss-cross overlapping pattern on the magnetictape storage medium.

Thus, the read-after-write head 100 provides four channels of read andwrite during the azimuthal mode of operation in both the forward andbackward directions of magnetic tape motion. This operation isselectively controlled in a well known manner by the tape recordercontrol system. As illustrated in FIG. 5, the azimuth mode typicallyproduces a criss-cross overlapping pattern on the magnetic tape storagemedium.

As illustrated in FIGS. 7 and 8, in the non-azimuth mode of operation,the read-after-write head 100 is indexed to a preselected position overthe selected tracks of the magnetic tape medium which is moving in aforward direction (as indicated by the arrow 605 in FIG. 7) relative tothe read-after-write head 100. The read-after-write head is then rotatedto, or maintained at, the neutral or laterally aligned angular positionillustrated in FIG. 7 (azimuth angle equals zero). In this position theforward write head gaps 106 and 110 (forward write channels two andfour) are substantially aligned with the longitudinal direction of themoving magnetic tape medium. Furthermore, the read head gaps 120 and 124(read channels one and three) are also substantially aligned with thelongitudinal direction of the moving magnetic tape medium and also inopposing relationship to the forward write head gaps 106 and 110(forward write channels two and four). The read-after-write head 100 maynow write to the tracks of the moving magnetic tape medium and/or readthe tracks of the magnetic tape medium in a well known manner

The tape direction is then selectively reversed to move the backwarddirection (opposite to the direction indicated by the arrow 605 in FIG.7). The read-after-write head 100 is again indexed to anotherpreselected position over the selected tracks of the magnetic tapemedium which is now moving in the backward direction (as indicated by adirection opposite to the arrow 605 in FIG. 7) relative to theread-after-write head 100. The read-after-write head is again maintainedin the neutral or vertical angular position as illustrated in FIG. 7. Inthis position, the backward write head gaps 114 and 118 (backward writechannels two and four) are substantially aligned with the longitudinaldirection of the moving magnetic tape medium. Furthermore, the read headgaps 120 and 124 (read channels one and three) are also substantiallyaligned with the longitudinal direction of the moving magnetic tapemedium and also in opposing relationship to the backward write head gaps112, 114, 116, and 118. The read-after-write head 100 may now write tothe tracks of the moving magnetic tape medium and/or read the tracks ofthe magnetic tape medium in a well known manner.

Thus, the read-after-write head 100 provides two channels of read (usingread channels one and three) and write (using forward and backward writechannels two and four) during the non-azimuthal (or vertical) mode ofoperation in both the forward and backward directions of magnetic tapemotion.

In summary, FIGS. 2-8 show the illustrative dual-mode method ofrecording data onto azimuthal and non-azimuthal magnetic tapes by usingthe read-after-write head 100. The illustrative method generallycomprises the steps of:

positioning the head 100 at a predetermined azimuth angle forfour-channel azimuth mode recording, and then

writing data onto a first magnetic tape in the four channel azimuth modeusing the read-after-write recording head 100, etc.; as well as

positioning the head 100 at the nominal, non-azimuth null position fortwo-channel non-azimuth recording, and then

writing data onto a second magnetic tape in two channel non-azimuth modeusing the read-after-write recording head 100, etc.

During azimuth mode bidirectional recording the method includes thesteps of positioning the head 100 at a positive predetermined angle forforward-direction four channel azimuth mode recording, and repositioningthe head 100 at a negative or complementary azimuth angle forbackward-direction four-channel azimuth mode recording, in addition tothe writing steps. In both modes, the head 100 advantageously performsreading after writing during each writing operation in order to verifythat the data pattern intended for writing has actually been recordedonto the tape.

The illustrative embodiment includes four forward write head gaps, fourread head gaps, and four backward write head gaps. It will be apparentto a person of ordinary skill in the art, having the benefit of thisdisclosure, that the teachings of the disclosure may provide aread-after-write head for azimuth and non-azimuth modes of operationwith any number and combination of read and write head gaps.

It will be appreciated by those of ordinary skill having the benefit ofthis disclosure that numerous variations from the illustrations in thenotes will be possible without departing from the inventive conceptdescribed herein.

What is claimed is:
 1. A tape recording apparatus, comprising:(a) a baseincluding means for transporting a magnetic recording tape along alongitudinal axis, (b) a controller; (c) a head mounting apparatussecured to a base and controlled by the controller; and, (d) aread-after-write head positioned by the head mounting apparatus toconfront the magnetic recording tape, said read-after-write head adaptedfor operation in azimuth and non-azimuth modes of operation by rotationto at least one positive azimuth angle for azimuth mode and to a nullangle for non-azimuth mode.
 2. The tape recorder apparatus of claim 1,wherein said read-after-write head is adapted for four-channel azimuthmode operation.
 3. The tape recorder apparatus of claim 1, wherein saidread-after-write head is adapted for two-channel non-azimuth modeoperation.